4plus1 models

4+1 Models (Core)

Generates Kruchten's 4+1 View Model for any software system.

This skill owns method logic only:

• invocation mode and audience routing
• context and concern capture
• per-view architecture content
• canonical diagram-as-code (Mermaid / PlantUML)
• cross-view consistency

It does not own output-track rendering mechanics for draw.io or Miro.

The five views at a glance

View	Who reads it	What it answers	Primary notation
Logical	End-users, analysts, architects	What components exist and how they relate	Mermaid class / component / C4 Container
Process	Integrators, performance engineers, operations, BAs	How the system behaves at runtime	Mermaid sequenceDiagram (dev) / flowchart with swimlanes (cross-functional)
Development	Developers, software managers	How the codebase is organised	Mermaid flowchart / C4 Component
Physical	SRE, infrastructure engineers	How it's deployed and operated	PlantUML deployment + AWS/Azure/GCP stdlib (primary) / Mermaid C4Deployment (fallback)
Scenarios (+1)	All stakeholders	Key use cases that exercise the other four	Mermaid flowchart (use-case style) + mini sequences

Reference files per view: references/logical-view.md, references/process-view.md, references/development-view.md, references/physical-view.md, references/scenarios-view.md.

Workflow

Step 1 — Determine invocation mode

Decide which mode the user is in. If ambiguous, ask.

• Zero-input mode — user gives a short description and expects a draft with explicit assumptions.
• Interview mode — user has real context and wants rigour.
• Partial mode — user wants only one or a subset of views.

Step 2 — Determine audience (ALWAYS ASK unless user pre-stated it)

Ask if missing:

"Who's the primary audience for this documentation? (a) Dev-only (b) Cross-functional (c) Executive"

Audience determines notation choice per view.

Step 3 — Gather system context

Gather context with one concise checklist first, then only targeted follow-ups if needed.

Start with at most these fields:

• System name and purpose
• Stakeholders and concerns
• Tech stack
• Scale profile
• Quality attributes
• Constraints
• Out of scope

Mark assumptions explicitly using > **Assumption:**.

Questioning rules:

• Keep the first interaction to one grouped question block.
• If the user gives partial info, proceed with assumptions rather than asking every missing detail immediately.
• Ask one follow-up at a time only when a missing answer blocks the next deliverable.
• Use plain wording and provide concise options where possible.

Step 4 — Route concerns into each view

Use concerns/README.md to select relevant concern modules.

Default concerns:

• gdpr-data-protection.md
• security.md
• bias-fairness.md (if ML present)
• regulatory-compliance.md (if regulated domain)

Step 5 — Generate each view

Generate in order:

1. Logical
2. Process
3. Development
4. Physical
5. Scenarios (+1)

Use templates/view-template.md.

Step 6 — Cross-view consistency check

Verify:

• consistent naming across views
• process behaviours map to deployable units
• scenarios exercise elements from core views

If writing to disk, run:

python scripts/validate-views.py <output-directory>

For example:

python scripts/validate-views.py docs/architecture

Step 7 — Output format (core)

[system-name]-architecture/
├── 00-system-context.md
├── 01-logical-view.md
├── 02-process-view.md
├── 03-development-view.md
├── 04-physical-view.md
├── 05-scenarios-view.md
└── diagrams/
    └── mermaid/
        ├── logical-view.mmd
        ├── process-view.mmd
        ├── development-view.mmd
        ├── physical-view.puml
        └── scenarios-view.mmd

When used inside the 4plus1-diagrams workflow, the visual-format skill adds a diagrams/drawio/ or diagrams/miro/ sibling folder alongside diagrams/mermaid/.

Quality standards

• No placeholders
• Diagram + prose for every view
• Rationale tied to quality attributes/constraints
• Audience statement at top of each view
• Visible assumptions
• Specific concerns only

Reference index

Per-view detail:

• references/logical-view.md
• references/process-view.md
• references/development-view.md
• references/physical-view.md
• references/scenarios-view.md

Notation cheatsheets:

• references/notation-mermaid.md
• references/notation-plantuml.md
• references/notation-bpmn-in-mermaid.md

Concerns:

• concerns/README.md
• concerns/gdpr-data-protection.md
• concerns/security.md
• concerns/bias-fairness.md
• concerns/regulatory-compliance.md
• concerns/sustainability-climate.md
• concerns/accessibility.md

Template:

• templates/view-template.md

Worked example (core views):

• examples/synth-claim/

Scripts:

• scripts/validate-views.py